When to Get Tested?

When a doctor suspects that someone with chest pain, coughing, and/or difficulty breathing has tuberculosis that has spread to their pleurae (lining around the lungs)

Sample Required?

A volume of pleural fluid is collected by a doctor using a procedure called thoracentesis; other body fluids are collected using other procedures

Test Preparation Needed?

None

The Test Sample

What is being tested?

Adenosine deaminase (ADA) is a protein that is produced by cells throughout the body and is associated with the activation of lymphocytes, a type of white blood cell that plays a role in the immune response to infections. Conditions that trigger the immune system, such as an infection by Mycobacterium tuberculosis, the bacteria that causes tuberculosis (TB), may cause increased amounts of ADA to be produced in the areas where the bacteria are present. This test measures the amount of adenosine deaminase present in pleural fluid in order to help diagnose a tuberculosis infection of the pleurae.

Pleurae are membranes that cover the chest cavity and the outside of each lung. Small amounts of pleural fluid are continuously produced to lubricate the movement of the lungs against these membranes and the membranes against each other during inhalation and exhalation. A variety of conditions and diseases, including infection, can cause inflammation of the pleurae (pleurisy or pleuritis) and can lead to excessive pleural fluid accumulation (pleural effusion).

Tuberculosis can spread into the lungs and pleurae, causing symptoms such as chest pain, chronic cough, and shortness of breath. Since these symptoms may also be seen with a variety of other conditions, it is important to determine the cause as rapidly as possible in order to properly treat the affected person. Detecting mycobacteria in pleural fluid can be difficult because there may be a large volume of fluid and very low numbers of bacteria present. Though the ADA test is not specific and does not replace the culture for diagnosing TB, it may be positive even when numbers of bacteria are very low and can be used as an adjunct test to help determine whether tuberculosis is the likely source of a person's symptoms.

How is the sample collected for testing?

A sample of pleural fluid is collected by a doctor with a syringe and needle using a procedure called thoracentesis. Rarely, other body fluid samples, such as peritoneal or CSF, are collected using procedures specific to the fluid type.

A culture is considered the "gold standard" for diagnosing tuberculosis and guiding treatment, but it may take several days to weeks to complete. Molecular testing and the AFB smear are rapid tests, but they require that a sufficient number of microorganisms be present in the fluid to detect them. Pleural fluid presents a unique problem with detecting M. tuberculosis because there may be a large volume of fluid with a very low number of bacteria present. Though the ADA test is not definitive, it is a rapid test and may be elevated even when there are few bacteria present. ADA results may be used to help guide treatment until results from a culture are available.

The ADA test is used as an adjunct test to help rule in or rule out tuberculosis in pleural fluid. Rarely, it may be ordered to detect tuberculosis in other body fluids, such as peritoneal fluid or cerebrospinal fluid (CSF).

People who work with or are part of groups with high rates of infection, such as the homeless, IV drug users or confined populations, such as hospitalized patients, prisoners, and residents of nursing homes

What does the test result mean?

If adenosine deaminase (ADA) is markedly elevated in pleural fluid in a person with symptoms that suggest tuberculosis, then it is likely that the person tested has a M. tuberculosis infection in their pleurae. This is especially true when there is a high prevalence of tuberculosis in the geographic region where a person lives.

When there is a low prevalence of tuberculosis in a region, then a person may have tuberculosis or may have an ADA result that is elevated for another reason, such as cancer (particularly lymphomas), pulmonary embolus, sarcoidosis, or systemic lupus erythematosus. These other diagnoses are more likely if the ADA result is only mildly or moderately elevated.

A person with a low ADA level is unlikely to have tuberculosis in their pleurae. This does not rule out having the infection in other parts of their body.

If ADA is markedly elevated in fluid from another part of the body (such as peritoneal fluid or CSF), then there is an increased likelihood that tuberculosis is present in this area.

The doctor cannot diagnose tuberculosis in the pleural space without testing the pleural fluid. If the infection is present in your lungs, then sputum may be collected, or if meningitis is suspected, CSF would be tested.

2. Should everyone with suspected tuberculosis have an ADA test performed?

The ADA test is primarily performed when tuberculosis is suspected in the pleurae, and it is not routinely available in all laboratories. It will be performed when a doctor determines that it will be useful and timely in helping to diagnose or rule out tuberculosis.

3. Can my blood be tested for ADA?

4. What is ADA deficiency?

ADA is an enzyme that converts one byproduct into another byproduct. The first substance is toxic to lymphocytes and must be inactivated by ADA. With ADA deficiency, a rare inherited condition, the body makes insufficient ADA. This leads to the buildup of the toxic byproduct and can cause severe combined immunodeficiency disease (SCID). Infants with this condition have seriously compromised immune systems and may not survive without bone marrow transplantation.

Ask a Laboratory Scientist

This form enables you to ask specific questions about your tests. Your questions will be answered by a laboratory scientist as part of a voluntary service provided by one of our partners, American Society for Clinical Laboratory Science. If your questions are not related to your lab tests, please submit them via our Contact Us form. Thank you.

* indicates a required field

First Name

Last Name

Please indicate whether you are a:

Patient, Family member or FriendLaboratorian or Other Medical ProfessionalOther

Your Email Address *

Confirm Your Email Address *

You must provide a valid email address in order to receive a response.

Article Sources

NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.

Proudly sponsored by ...

Learn more about ...

Get the Mobile App

Follow Us

This article was last reviewed on May 18, 2012. | This article was last modified on October 8, 2014.

The review date indicates when the article was last reviewed from beginning to end to ensure that it reflects the most current science. A review may not require any modifications to the article, so the two dates may not always agree.

The modified date indicates that one or more changes were made to the article. Such changes may or may not result from a full review of the article, so the two dates may not always agree.